"Green amethyst" is the trade name for prasiolite, a green variety of quartz. Most prasiolite is created by heat-treating purple amethyst, but naturally occurring prasiolite is extremely rare. 
Origin and formation
Most prasiolite sold today is treated rather than natural. 
Benefits and metaphysical properties
In the world of spiritual healing, smooth green amethyst (prasiolite) is believed to possess calming, transformative, and heart-opening energies. 
Uses in jewelry
With a Mohs hardness of 7, prasiolite is durable enough for daily wear in many types of jewelry. Its minty-green color makes it an attractive and versatile gemstone. 
Care for green amethyst jewelry